1. Field of the Invention
The present invention relates to a processing apparatus and method for fluid, and a deaerator with the apparatus.
2. Background of the Invention
To begin with, description is made of the conventional art for the processes of dispersion and emulsification.
There have been widely used dispersing systems generally called “media mill” in the producing systems for coating medium, inks, magnetic materials, ceramics, cells, adhesives, electronic materials, liquid crystal color filters, medicines, cosmetics, perfumes, foods, etc. This specific dispersing system is intended to obtain desired dispersion of fluid being processed by agitating said fluid being processed in the dispersion chamber filled with beads, sand, or balls, as called media, to apply a shear force, and impact to said fluid for dispersion.
As a first disadvantage consisting in this system, during process, friction between media, between the media and the agitating blades of the apparatus, between the media and the inner side of a container may bring about some chips ground from said matters so that said chips will be mixed into said fluid as impurity. As a result, frequent supplement of loss due to friction with fresh media and exchange of parts are needed, thus entailing extra troubles and cost accordingly.
A second disadvantage is that application of a stronger shear force or demand of smaller particle diameter requires the use of media of smaller diameter than those in the past, for example, use is often made of fine media in the size of 0.05 or 0.1 millimeter in diameter, and there is a tendency to seek for media of relatively small diameter. However, the smaller the diameter of media, the smaller the mass of each medium, which may cause decrease of the dispersible range of viscosity of the fluid to be processed with the consequence that only a substance of low viscosity is applicable.
Meanwhile, a roll mill and a colloid mill are known except for said media mill.
The colloid mill acts to give a shear force to the fluid to be processed by passing said fluid through the interval formed between two disks laid one upon another. In this case, the width of the interval can be determined mechanically by means of an adjusting handle, but the apparatus used is only capable of adjusting on the level of substantially more than several dozen microns (no adjustment was possible as to the level of less than 10 microns). Further reduction of the width may incur the risk of a serious accident on account of the contacts of the disks as occurred by thermal expansion or run-out of the rotary shaft.
The roll mill acts to apply a shear force to said fluid by rotating two or three rolls at different speeds and in different directions, respectively. The width of the interval between said rolls may be regulated mechanically. Also in this event, as in the case of the colloid mill, it is hard to adjust the width at the level of scores of micron. And it is necessary to provide adequate crowns for further regulation of the pressure occurring between the rolls, which operation needs human skills and involves risks of accidents. Moreover, the apparatus itself remains so opened that it is not useful for fluid containing rather evaporable solvent. As both the colloid mill and the roll mill are dependent on stronger intervals for efficient application of a shear force to fluid to be processed, which should be of a high viscosity.
Furthermore, a high-speed rotary homogenizer and a high-pressure homogenizer are also known. The former is employed as a pre-dispersing unit, but it is unavailable for precise dispersion. The latter is known that when used as industrial equipmentit, it is endowed with too many difficulties such as wear and tear of the orifice portion or stopping of capillary as well as seal wear of the booster pump.
In this connection has been sought for the development of a dispersing apparatus arranged such that inclusion of impurity can be avoided, a stronge shear force can be given to fluid having a wider application range of viscosity, and dispersion, emulsification and crushing can be performed at a high precision.
Next, the conventional art for attrition and pulverization will be described.
Conventional pulverizers based on hand mill principles include a pair of whetstones that are laid one upon another and adjustable in the interval therebetween, wherein a strong centrifugal force, an impact grinding force and shear are produced between said whetstones, thus a combined action of them performs attrition and pulverization. The attrition or pulverizing apparatuss provided with rotatable and/or stationary whetstones are disclosed by the following official gazette.                Patent document 1: Japanese (JP) design registration No. 655304        Patent document 2: JP design registration No. 845632        Patent document 3: JP examined patent application publication No. S62-51658        Patent document 4: JP examined patent application publication No. H03-1061        Patent document 5: JP examined patent application publication No. H04-55830        
A rotary or stationary whetstone used here is generally called grinders, commonly having particle sizes 16#, 24# to 120#, and 240#. Though having different particle sizes, these grinders are uneven on the surface, and when they handle hard a substance to be processed, there is possibility that raised portion will be scraped or worn out to cause inclusion of impurity.
It has been reported that the grinding apparatus as disclosed in the following patent document 6 is capable of grinding a material into fine particles of the order of 1 to 5 microns, but it is unable to obtain fine particles of under 1 micron with said apparatus.                Patent document 6: JP examined patent application publication No. S62-51658        
There is a report relating to the grinding system as disclosed by the following patent document 7. According to the report, in pulverization of a substance to be processed that contains high fat, much moisture, high protein, sugar, and specific enzymes, such particular properties tend to change because of stickiness, scorching, or transformation into film due to frictional heating, so that said substance are not marketable as in the form of powder. And if the peripheral velocity of the rotary whetstone has risen above a certain level, grinding ability thereof is rapidly increased, concurrently with the temperature rise due to frictional heat decreasing its degree, and when the peripheral velocity of 3,422 meters per minute has reached, problems in machine cost and mechanical security occur.                Patent document 7: JP laid-open patent Application No. H07-185372        
Furthermore, the following patent document 8 discloses an automated controlling method for the clearance between the rotary and stationary whetstones. In this particular method, mechanical heat build-up occurs from the high-speed rotation, but in the absence of a buffer system for thermal expansion of the driving shaft and for run-out of the rotary whetstone, the minimum clearance is liable to widen over dozens of microns.                Patent document 8: JP laid-open patent application No. H08-1020        
The following patent document 9 discloses the invention useful for grinding, dispersion and emulsification of fluid to be processed, in particular liquid. However, a fluid pressure applying mechanism for fluid and a head pressure are needed for processing the fluid.                Patent document 9: JP patent application No. 2002-207533        
After all, in the event of supplying a material to be processed under the atmospheric pressure, each of the aforementioned systems are incapable of narrowing the clearance between the two whetstones (grinding members) laid one upon another to less than 15 microns. Namely, the foregoing clearance between the whetstones by means of the conventional mechanical means can not be suitable for micro-scale attrition or grinding. Meanwhile, the use of said mills for attrition and grinding operations may cause inclusion of foreign substances (chips resulting from the contact between the mills or the mill and other matters), and a grinding apparatus which may safely rotate at high speed for high performance is not available.
Here, description will be made of a conventional art for deaerating process.
Deaerators for a substance to be processed involve, for example, a unit that serves to remove bubbles from liquid.
This bubble removing unit comprises an external cylindrical rotor disposed within a vacuum vessel, an internal cylindrical rotor arranged in concentric alignment with the external rotor in the interior of said external rotor, and a hollow shaft driven for revolution by motor, the internal rotor being connected with said shaft and rotating in respect of the external rotor.
The peripheral face of said internal cylindrical rotor may be composed of a punching plate. The peripheral face of said external cylindrical rotor may be constituted of a screen of finer surface texture than that of said punching plate.
Next, the action of this bubble removing unit will be explained.
Said shaft has a passage for liquid to be processed thereinside. Said liquid travels through the shaft into the internal rotor. By the passage of liquid through the shaft rotating at high speed, the liquid phase is centrifuged toward the inner wall of the shaft, and bubbles toward the center of the shaft. At this time, prior to the liquid phase, the bubbles are drawn toward the center of the shaft, expanding before deaerated.
In said liquid phase as introduced into the internal rotor after said motion of the bubbles, the centrifugal force caused by the rotary motion effects film formation, which may forward the removal of bubbles. Then, the liquid phase passes through the punching plate of the internal rotor until it has been subjected to atomization, which may promote deaeration. Having passed through the punching plate, the liquid gets in contact with the external rotor, and passes through the screen. Then, the liquid is scattered in a spray within the vacuum, hitting the inner wall of the vessel to fall down along the inner wall before the termination of the removal of bubbles.
This particular bubble removing unit may chiefly perform atomization of substance by allowing the substance to pass through said punching plate and screen. Such atomization acts to promote emission of bubbles contained in the substance, and said unit may achieve smooth deaeration by the use of such action.
The size of bubbles resulting from the atomization is highly dependent on the fine texture of the punching plate and screen.
The fine division of the textures of the punching plate and screen has a physical limit, so that they are not useful for removal of bubbles much finer than the textures of the punching plate and screen. That is, with the bubble removing unit of the described construction, 10 to 20 microns is the limit of fine division, therefore, super fine division into 1 to 2 microns was impossible.
If a substance to be processed was emulsion or suspension, it was necessary to deaerate by means of said bubble removing unit the substance which had been emulsified or suspended, for example, through a high-speed agitating or dispersing unit in advance.
As the textures of the punching plate and screen are so smudged by the previous process operation that they may clog up, prior to use of said bubble removing unit for the next operation, the punching plate and screen must be cleaned sufficiently.
Said punching plate and screen cause nuisance of cleaning and removing of clogs thereof.
The present invention has been made based on said status of dispersion and emulsification processes, which invention may provide a dispersion and emulsification apparatus of a simple structure and high productivity, which is capable of making dispersion, emulsification, and shattering with high precision, on the basis of a unique idea of making use of the mechanical seal mechanism as means of dispersion and emulsification for solution of the foregoing problems.
That is, the object of the present invention is to provide a dispersion and emulsification apparatus which may prevent inclusion of impurity, and make highly precise dispersion, emulsification, and shattering.
In particular, the further object of the present invention is to provide a dispersion and emulsification apparatus which can set a predetermined width at the interval of the clearance between two processing faces relatively rotatable to each other, and furnish fluid to be processed with a strong shear force.
Another object of the present invention is to provide a dispersion and emulsification apparatus which can process a wide range of viscosity for fluid to be processed.
Additionally, for the purpose of solution of the abovementioned problems, the present invention provides a grinding apparatus which performs grinding that is absolutely required in the recent development of nanotechnology. Namely, the grinding apparatus makes it possible to perform highly precise grinding, preventing any inclusion of impurity, having a simple structure for ensuring high safety, and being manufactured at a low cost. Furthermore, the grinding apparatus may act to constantly grind a substance between two whetstones to a particle below a micron size, and cope with a wide range of substances in terms of the form and size of particles, specific gravity, degree of moisture, and various natures and properties of substances consisting of several kinds of particles which are different in form, size, specific gravity, degree of moisture.
Moreover, for solution of said problems, the present invention is made based on said circumstances for deaerating process to provide a deaerator including an atomizing mechanism totally different from said conventional counterparts, so that removal of micro-scale bubbles, which was not available in the past, can be performed by atomizing a substance to a finer degree. The deaerator may avoid the necessity of troublesome cleaning operation for punching plates and screens.